Wednesday, June 6, 2007

Choosing Binoculars

What you want to see will really help in determining which binoculars you want to purchase. Wide angle binoculars (which can see a larger area), are usually about 6x, 7x or 8x magnification. This is the first number in the series. The higher the number, the smaller the area you can see, but the further and more crisp the image will be. Smaller numbers, like 7x and 8x, give you a larger field of view, while larger numbers like 10x and more give you a much smaller field of view.

The problem with going higher than 8x is that it is very hard to keep the image in view, as even the slightest shake of your hands will send you miles away from your object. If you are trying to see things really far away, like the moon and tightly knit constellations, you will want a higher magnification, but will need a tripod or other device to keep the binoculars still. You can also rest your elbow on the hood of your car to keep it steady, but its more difficult for children to do this. If you are wanting to see birds in flight, a lower magnification is better as you can actually follow them with your binoculars quite well. Choose a number around 7x for this.

The second number determines how much light is gathered into the binoculars. The higher the number, the more light will be gathered and the larger the exit pupils. If you will be using the binoculars at night, you need larger exit pupils (corresponding to a higher last number). If you will only be using them during the day, you can have smaller exit pupils - as you don't need a ton of light to be gathered into the binoculars. This is best for those who are carrying the binoculars around - like on nature hikes and sporting events. Remember, the larger front does not correspond with how much you see, it corresponds with how much light you need to be pulled into the binoculars. Think of it like an owls eyes - owls have big eyes because they need to gather in lots of light to see so well at night (actually their rod cone cells are really responsible for night vision, but larger eyes aid in this endeavor).

Binoculars used for astronomy are usually larger, heavier, with huge (about 50x) exit pupils, and they need to be stabilized with a tripod. The larger magnification (10x is good for astronomy), again, brings far away objects into clear focus, but are also harder to keep trained on the object with your bare hands - your hands shake just enough to make it difficult to keep it focused on one spot. If the object is moving at all, you will not be able to follow it.

Binoculars used for plays, sporting events and nature hikes are smaller, both with magnification and exit pupils, the wider angle (smaller magnification) allows them to follow the moving person or animal, the smaller exit pupil is easier to handle and tote around. But if you plan to go to night events, you may want to get a small magification (smaller first number) and larger exit pupils (higher second number).
So, you see, what binoculars look like does not determine how good they are - it determines their purpose.

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